Definitely look for down and away but be able to foul of fastballs on the inner half. Maybe a perfect inside FB on the black can beat you but you need to be able to foul off a fastball that is middle in unless you have a read that the P always goes soft stuff away with 2 strikes.
I also think you should dare the ump to call you out on high fastballs. Of course this doesn't mean taking a waist high fastball but try to shrink the top of the zone an inch or two because many umps don't like to call the high strike (especially at higher levels) and by shrinking the top a little and looking down you also are less likely to swing at the classic 0-2 high chase fastball.